Carrier 25VNA Service Manual page 23

Start
Verify motor
temp fault
condition at the
system controller
Is the system
A
operable ?
Yes
No
WARNING !
Disconnect &
lock- out power,
C
allow 2 minutes
for drive to
discharge
Disconnect
yellow, black,
and red wires
from output
connections on
drive (See Fig. 23)
Verify motor
winding
continuity from
the yellow, black,
and red lead
ends
Check each leg
(yellow, black,
and red wires) to
ground
If any of the
above Ω readings
show open or
short to ground,
replace the plug
Measure
Disconnect 4-pin resistance
plug from drive between red &
(See Fig. 18) white wires in the
4-pin plug
Measure
resistance
between unit
Is resistance
ground and
459Ω to 168KΩ ?
black, white, &
red wires in the
plug
No
Is compressor
Is there continuity
hot ?
No
to ground ?
Yes
Yes
Allow time for
compressor to
B
cool & resistance
to change (60
minutes )
Measure
resistance
between red &
white wires in the
4-pin plug
Is resistance
459Ω -168KΩ?
No
Refer to
thermistor
resistance -
temperature data
Fig. 14 – Motor Temp Fault Troubleshooting - - Part 1
Resistance
is in range
that will A
Yes
allow
operation
Refer to
thermistor
resistance -
No
temperature data
(See Fig. 15)
Is resistance
0Ω?
Yes
No
Allow time for
resistance to
change (60
minutes )
A
Yes
Power down the
Is Ω moving towards
entire system for
Ω corresponding to
2 minutes to
ambient temp ?
reboot the drive
No
Yes
If problem still
exists, change
the compressor
23
Thermistor
circuit is
shorted
WARNING !
Recover system
refrigerant
charge
Remove the
molded plug from
the thermistor
fusite on the
compressor
(See Fig. 19)
Measure
resistance in
motor thermistor
circuit pins
(See Fig. 20 & 21)
Motor thermistor
circuit is shorted
Is resistance
internally - replace
Yes
0Ω?
compressor
No
Inspect molded
plug assembly
for lead to lead
shorting
Install new
molded plug
assembly and
carefully route
wires
A
A11554